in-line flow restriction/energy dissipation in sewer pipe

[amaya]

We are designing a sanitary sewer network on a new residential development. Within this development there is a steep slope (a drop of 25 meters in elevation over a length of 200 meters).the sewage would have to travel through this steep area. We were able to design and allocate a series of manholes to meet the maximum slope of 7% and maximum velocity of 10 feet per second (according to specification). We found out that because of the terrain in this particular area is going to be very expensive. So we were looking at installing sewer pipe/pipes to achieve a continuous flow. The problem with that is how we control the flow so it doesn’t exceed the 10 fps. In other word how do we dissipate the energy or control the kinetic energy. Can we have a venture tubing system or maybe a high velocity manhole at the bottom of the hill to withstand the kinetic energy? Any suggestion ?

 

[RWF7437]

Why not post this in the wastewater forum ?

 

[amaya]

thank you.

 

[ngneer]

i am currently facing a similar design problem. Without more detail about "how expensive" excavating within the steep slope material will be, I can only suggest the solution with additional drop manholes to reduce flow velocity. Also, you may want to utilize a material such as ductile iron versus pvc if flow (Q) is quite high. Fortunately for my design the neighborhood is currently utilizing septic tanks, and very few homes will connect. Thus, the predicted velocity will not be too excessive and pipe scour / manhole energy loss will not be a significant maintainance concern. I might also caution that future development should be considered. Although the pipe may only flow 10% full at construction with lower velocity, future use could pose concerns.

 

[dicksewerrat]

Check with 'red Valve' They make passive valves that should fit inside a few of the pipes.